Premarital sexual relations are becoming more common in Africa, a trend which is especially prevalent in urban settings. Although unmarried youth increasingly use condoms, many studies highlight considerable unmet contraceptive needs in this population subgroup. This article is based on qualitative data gathered in 2006 and 2007 in Ouagadougou, Burkina Faso, through 77 in-depth interviews with young women and men conducted for the Emergency Contraception in Africa (ECAF) survey. The authors show how unequal gender relations lead to unplanned premarital pregnancies. As in the past, young women's sexual activity before marriage is marked by a quest for morality and marriage, even if marriage is postponed. Male premarital sexual activity is often characterized by the positive value attached to multiple partners and to men's pleasure. These contrasting rationales for premarital sex can lead individuals either to seek ways of avoiding pregnancy at all costs or to neglect prevention. Unplanned pregnancies occur when one of the two partners adheres to more than one rationale and/or when the two partners adhere to different rationales. In the latter case, the asymmetry between men's and women's motivations weakens women's bargaining power over the use of condoms.